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Commit 1a08de99 authored by Vincent Pelletier's avatar Vincent Pelletier
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Reindent mq.py with 4 spaces. 


git-svn-id: https://svn.erp5.org/repos/neo/branches/prototype3@925 71dcc9de-d417-0410-9af5-da40c76e7ee4
parent 8efbb110
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neo/client/mq.py
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......@@ -33,231 +33,231 @@ Multi-Queue Cache Algorithm.
from math import log
class Element(object):
"""
This class defines an element of a FIFO buffer.
"""
pass
"""
This class defines an element of a FIFO buffer.
"""
pass
class FIFO(object):
"""
This class implements a FIFO buffer.
"""
def __init__(self):
self._head = None
self._tail = None
self._len = 0
def __len__(self):
return self._len
"""
This class implements a FIFO buffer.
"""
def append(self):
element = Element()
element.next = None
element.prev = self._tail
if self._tail is not None:
self._tail.next = element
self._tail = element
if self._head is None:
self._head = element
self._len += 1
return element
def __init__(self):
self._head = None
self._tail = None
self._len = 0
def __len__(self):
return self._len
def append(self):
element = Element()
element.next = None
element.prev = self._tail
if self._tail is not None:
self._tail.next = element
self._tail = element
if self._head is None:
self._head = element
self._len += 1
return element
def head(self):
return self._head
def tail(self):
return self._tail
def shift(self):
element = self._head
if element is None:
return None
del self[element]
del element.next
del element.prev
return element
def __delitem__(self, element):
if element.next is None:
self._tail = element.prev
else:
element.next.prev = element.prev
def head(self):
return self._head
if element.prev is None:
self._head = element.next
else:
element.prev.next = element.next
def tail(self):
return self._tail
def shift(self):
element = self._head
if element is None:
return None
del self[element]
del element.next
del element.prev
return element
self._len -= 1
def __delitem__(self, element):
if element.next is None:
self._tail = element.prev
else:
element.next.prev = element.prev
if element.prev is None:
self._head = element.next
else:
element.prev.next = element.next
self._len -= 1
class Data(object):
"""
Data for each element in a FIFO buffer.
"""
pass
"""
Data for each element in a FIFO buffer.
"""
pass
def sizeof(o):
"""This function returns the estimated size of an object."""
if isinstance(o, tuple):
return sum((len(s)+16 for s in o))
else:
return len(o)+16
"""This function returns the estimated size of an object."""
if isinstance(o, tuple):
return sum((len(s)+16 for s in o))
else:
return len(o)+16
class MQ(object):
"""
This class manages cached data by a variant of Multi-Queue.
This class caches various sizes of objects. Here are some considerations:
"""
This class manages cached data by a variant of Multi-Queue.
This class caches various sizes of objects. Here are some considerations:
- Expired objects are not really deleted immediately. But if GC is invoked too often,
it degrades the performance significantly.
- If large objects are cached, the number of cached objects decreases. This might affect
the cache hit ratio. It might be better to tweak a buffer level according to the size of
an object.
- Stored values must be strings.
- The size calculation is not accurate.
"""
- Expired objects are not really deleted immediately. But if GC is invoked too often,
it degrades the performance significantly.
def __init__(self, life_time=10000, buffer_levels=9, max_history_size=100000, max_size=20*1024*1024):
self._history_buffer = FIFO()
self._cache_buffers = []
for level in range(buffer_levels):
self._cache_buffers.append(FIFO())
self._data = {}
self._time = 0
self._life_time = life_time
self._buffer_levels = buffer_levels
self._max_history_size = max_history_size
self._max_size = max_size
self._size = 0
- If large objects are cached, the number of cached objects decreases. This might affect
the cache hit ratio. It might be better to tweak a buffer level according to the size of
an object.
def has_key(self, id):
if id in self._data:
data = self._data[id]
if data.level >= 0:
return 1
return 0
- Stored values must be strings.
__contains__ = has_key
- The size calculation is not accurate.
"""
def __init__(self, life_time=10000, buffer_levels=9, max_history_size=100000, max_size=20*1024*1024):
self._history_buffer = FIFO()
self._cache_buffers = []
for level in range(buffer_levels):
self._cache_buffers.append(FIFO())
self._data = {}
self._time = 0
self._life_time = life_time
self._buffer_levels = buffer_levels
self._max_history_size = max_history_size
self._max_size = max_size
self._size = 0
def fetch(self, id):
"""
Fetch a value associated with the id.
"""
data = self._data[id]
if data.level >= 0:
value = data.value
self._size -= sizeof(value) # XXX inaccurate
self.store(id, value)
return value
raise KeyError(id)
def has_key(self, id):
if id in self._data:
data = self._data[id]
if data.level >= 0:
return 1
return 0
__getitem__ = fetch
__contains__ = has_key
def fetch(self, id):
"""
Fetch a value associated with the id.
"""
data = self._data[id]
if data.level >= 0:
value = data.value
self._size -= sizeof(value) # XXX inaccurate
self.store(id, value)
return value
raise KeyError(id)
__getitem__ = fetch
def get(self, id, d=None):
try:
return self.fetch(id)
except KeyError:
return d
def _evict(self, id):
"""
Evict an element to the history buffer.
"""
data = self._data[id]
self._size -= sizeof(data.value) # XXX inaccurate
del self._cache_buffers[data.level][data.element]
element = self._history_buffer.append()
data.level = -1
data.element = element
del data.value
del data.expire_time
element.data = data
if len(self._history_buffer) > self._max_history_size:
element = self._history_buffer.shift()
del self._data[element.data.id]
def store(self, id, value):
cache_buffers = self._cache_buffers
try:
data = self._data[id]
level, element, counter = data.level, data.element, data.counter + 1
if level >= 0:
del cache_buffers[level][element]
else:
del self._history_buffer[element]
except KeyError:
counter = 1
# XXX It might be better to adjust the level according to the object size.
level = min(int(log(counter, 2)), self._buffer_levels - 1)
element = cache_buffers[level].append()
data = Data()
data.id = id
data.expire_time = self._time + self._life_time
data.level = level
data.element = element
data.value = value
data.counter = counter
element.data = data
self._data[id] = data
self._size += sizeof(value) # XXX inaccurate
del value
def get(self, id, d=None):
try:
return self.fetch(id)
except KeyError:
return d
self._time += 1
def _evict(self, id):
"""
Evict an element to the history buffer.
"""
data = self._data[id]
self._size -= sizeof(data.value) # XXX inaccurate
del self._cache_buffers[data.level][data.element]
element = self._history_buffer.append()
data.level = -1
data.element = element
del data.value
del data.expire_time
element.data = data
if len(self._history_buffer) > self._max_history_size:
element = self._history_buffer.shift()
del self._data[element.data.id]
def store(self, id, value):
cache_buffers = self._cache_buffers
# Expire old elements.
time = self._time
for level in xrange(self._buffer_levels):
cache_buffer = cache_buffers[level]
head = cache_buffer.head()
if head is not None and head.data.expire_time < time:
del cache_buffer[head]
data = head.data
if level > 0:
new_level = level - 1
element = cache_buffers[new_level].append()
element.data = data
data.expire_time = time + self._life_time
data.level = new_level
data.element = element
else:
self._evict(data.id)
try:
data = self._data[id]
level, element, counter = data.level, data.element, data.counter + 1
if level >= 0:
del cache_buffers[level][element]
else:
del self._history_buffer[element]
except KeyError:
counter = 1
# XXX It might be better to adjust the level according to the object size.
level = min(int(log(counter, 2)), self._buffer_levels - 1)
element = cache_buffers[level].append()
data = Data()
data.id = id
data.expire_time = self._time + self._life_time
data.level = level
data.element = element
data.value = value
data.counter = counter
element.data = data
self._data[id] = data
self._size += sizeof(value) # XXX inaccurate
del value
# Limit the size.
size = self._size
max_size = self._max_size
if size > max_size:
for cache_buffer in cache_buffers:
while size > max_size:
element = cache_buffer.shift()
if element is None:
break
data = element.data
del self._data[data.id]
size -= sizeof(data.value) # XXX inaccurate
del data.value
if size <= max_size:
break
self._size = size
self._time += 1
# Expire old elements.
time = self._time
for level in xrange(self._buffer_levels):
cache_buffer = cache_buffers[level]
head = cache_buffer.head()
if head is not None and head.data.expire_time < time:
del cache_buffer[head]
data = head.data
if level > 0:
new_level = level - 1
element = cache_buffers[new_level].append()
element.data = data
data.expire_time = time + self._life_time
data.level = new_level
data.element = element
else:
self._evict(data.id)
# Limit the size.
size = self._size
max_size = self._max_size
if size > max_size:
for cache_buffer in cache_buffers:
while size > max_size:
element = cache_buffer.shift()
if element is None:
break
data = element.data
del self._data[data.id]
size -= sizeof(data.value) # XXX inaccurate
del data.value
if size <= max_size:
break
self._size = size
__setitem__ = store
__setitem__ = store
def invalidate(self, id):
if id in self._data:
data = self._data[id]
if data.level >= 0:
del self._cache_buffers[data.level][data.element]
self._evict(id)
return
raise KeyError, "%s was not found in the cache" % id
def invalidate(self, id):
if id in self._data:
data = self._data[id]
if data.level >= 0:
del self._cache_buffers[data.level][data.element]
self._evict(id)
return
raise KeyError, "%s was not found in the cache" % id
__delitem__ = invalidate
__delitem__ = invalidate
# Here is a test.
......
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